The invention relates to a method and to a device for applying adhesive threads onto a substrate. It also relates to a material web comprising an adhesive-thread fleece and an adhesive-thread layer. It also relates to products made from this web. It is used in a plurality of technical fields, e.g., in fixing powdery substances onto a base, such as a filter paper or filter cloth, in stone-wool coating, in hygienic products, such as diapers and sanitary napkins, in textile lamination, in carpet coatings, as anti-slip application, in paper bonding, such as paper towels, toilet paper, or paper napkins, and many more.
It is known to make fine and very fine adhesive threads in such a way that the liquid adhesive, for a hot melt bonding agent the fusible adhesive, is pressed through a nozzle duct. At the outlet of the still relatively large caliber adhesive thread, an extension in the longitudinal direction and swirling of the adhesive thread occur in such a way that the adhesive thread emerging from the nozzle is gripped by an air vortex by means of suitably arranged air-guidance ducts. The air nozzles are directed so that the thread performs an approximately spiral-shaped movement. The strand formed in this way is deflected by a spray application onto the substrate to be overlaid with an adhesive thread pattern. Through the use of air, the adhesive thread is cooled on its path between the nozzle and substrate. Therefore, the air must be greatly heated, which requires a lot of energy for a large surface-area adhesive application and is expensive. And only small heating of the adhesive thread, as a rule, has an effect only on a part of its flight path, so that the adhesive thread may already be noticeably cooled when it strikes the substrate. The spraying air, which likewise has a directional component toward the substrate, must be deflected back when striking the substrate if the substrate is not sufficiently permeable to air. Therefore, a kind of air cushion is created above the substrate, which supports the very light, drawn-out adhesive thread when it sinks onto the substrate, so that the thread can be only placed on the substrate where this air-cushion effect is sufficiently weak, thus, in the edge zones. Another disadvantage of the air spraying system (other gaseous media can also be used instead of air) is that very small application weights per substrate surface area of, e.g., one to five grams per m2 are barely possible. The fineness of the meshwork of the adhesive threads deposited onto the substrate is also relatively coarse because the adhesive threads always overlap in the edge region. In a spray application, this leads to the formation of strips and an excess of adhesive in the edge region of the adhesive application.